Thermal energy recovery system for an ice making plant of an ice rink

ABSTRACT

A thermal energy recovery system for an ice making plant of an ice rink includes a refrigeration unit for generating temperatures suitable for maintaining an ice surface that generates low grade heat as a by-product. A storage tank for storing a heat transfer fluid is provided. A refrigeration loop conveys heat transfer fluid containing low grade heat from the refrigeration unit to the storage tank. A thermal energy utilization loop provides fluid communication from the storage tank to a building HVAC system. There is at least one heat pump on the thermal energy utilization output conduit adapted to take heat transfer fluid containing low grade heat and convert the low grade heat into one of high grade heat or comfort cooling for use in the building HVAC system.

FIELD

The present application relates to a system for recovering thermal energy, specifically thermal energy generated by an ice plant of an ice rink, and using the recovered thermal energy elsewhere, such as a heating system.

BACKGROUND

Refrigeration demand on an ice making plant for an ice rink is cyclical; for example, for 20 to 25 minutes every 75 minutes. This results in there being available low grade heat having a temperature of less than 110 degrees Fahrenheit recoverable from the circulating heat transfer fluids. On the other hand, the building housing the ice surface requires a constant flow of high grade heating or cooling, depending on the season. Low grade heat recovered from an ice making plant for an ice rink is not of sufficient quality to meet typical building heating needs.

SUMMARY

There is provided a thermal energy recovery system for an ice making plant of an ice rink including a refrigeration unit for generating temperatures suitable for maintaining an ice surface and generating low grade heat as a by-product, the refrigeration unit having a fluid input and a fluid output. A storage tank stores a heat transfer fluid. A refrigeration loop has a refrigeration output conduit connecting the fluid output of the refrigeration unit to the storage tank such that heat transfer fluid containing low grade heat from the refrigeration unit is conveyed to the storage tank, and a refrigeration input conduit connecting the fluid input of the refrigeration unit to the storage tank. There is at least one circulation pump on the refrigeration loop adapted to circulate heat transfer fluid from the storage tank through the refrigeration unit. A thermal energy utilization loop has a thermal energy utilization output conduit providing fluid communication from the storage tank to a building HVAC system, and a thermal energy utilization return conduit providing fluid communication from the building HVAC system back to the storage tank. There is at least one circulation pump on the thermal energy utilization loop adapted to circulate heat transfer fluid containing low grade heat from the storage tank through the building HVAC system. There is at least one heat pump on the thermal energy utilization output conduit adapted to take heat transfer fluid containing low grade heat and convert the low grade heat into one of high grade heat or comfort cooling for use in the building HVAC system.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:

FIG. 1 is a schematic of a thermal energy recovery system for an ice making plant of an ice rink.

FIG. 2 is a simplified control system for the system shown in FIG. 1.

DETAILED DESCRIPTION

A thermal energy recovery system for an ice making plant of an ice rink generally identified by reference numeral 10, will now be described with reference to FIGS. 1 and 2.

Structure and Relationship of Parts:

Referring to FIG. 1, thermal energy recovery system 10 includes a refrigeration unit 12 for generating temperatures suitable for maintaining an ice surface. As a by-product, refrigeration unit 12 generates low grade heat. Refrigeration unit 12 includes a chiller 14 for removing heat from a secondary refrigerant by a primary refrigerant circulating between chiller 14 and a condenser 16, of which there may be more than one. Chiller 14 receives warmed secondary refrigerant from a refrigerant return conduit 18, which is then cooled by the primary refrigerant and returned to the cold floor 19 by way of refrigerant supply conduit 20. Condenser 16 in refrigeration unit 12 also transfers the low grade heat to a heat transfer fluid, which flows into condenser 16 of refrigeration unit 12 through fluid input 22 and out again through fluid output 24. The heat transfer fluid is stored in a storage tank 26. The actual size, and the number of tanks used, will depend on the amount of heat transfer fluid to be stored, and the heating/cooling demands of the installation.

Storage tank 26 is connected to refrigeration unit 12 by a refrigeration loop 30 having a refrigeration output conduit 32 connecting fluid output 24 of refrigeration unit 12 to storage tank 26, and a refrigeration input conduit 34 connecting fluid input 22 of refrigeration unit 12 to storage tank 26. In this way, heat transfer fluid containing excess low grade heat from refrigeration unit 12 is conveyed to storage tank 26. Throughout the system, circulation pumps are used to circulate the heat transfer fluid and refrigerants, and are labelled 36A through 36G. Circulation pump 36A on refrigeration loop 30 is adapted to circulate the heat transfer fluid from storage tank 26 through refrigeration unit 12. As shown, circulation pump 36A is connected to refrigeration input conduit 34.

On the other side of storage tank 26 is shown a thermal energy utilization loop 40 having a thermal energy utilization output conduit 42 and a thermal energy utilization return conduit 44. Output conduit 42 provides fluid communication from storage tank 26 to a building HVAC system 46, and return conduit 44 provides fluid communication from building HVAC system 46 back to storage tank 26. Another circulation pump 36E is shown on output conduit side 42 of thermal energy utilization loop 40, which is adapted to circulate heat transfer fluid containing low grade heat from storage tank 26 through building HVAC system 46. Heat pumps 50 are also on thermal energy utilization output conduit 42, which have a heating mode and a cooling mode. In the heating mode, heat pumps 50 take the heat transfer fluid and convert the low grade heat into high grade heat. In the cooling mode, heat pumps 50 take the heat transfer fluid and convert the low grade heat into comfort cooling. There may also be a dehumidifier 52, an underfloor heater 54, and a snow melt pit 56, which would be connected on thermal energy utilization loop 40. Circulation pumps 36G would be used to circulate the heat transfer fluid to these devices. These devices are known to those skilled in the art, and other devices may be present depending on the actual situation. These may be connected in parallel or in series with heat pumps 50. It will be understood that the actual configuration of the various elements that are connected thermal energy utilization loop 40 will depend on the physical locations, efficiencies of the elements, and other such factors known in the art.

As the heat transfer fluid passes through refrigeration unit 12, it picks up heat energy. As it passes through thermal energy utilization loop while heat pumps 50 are in the heating mode, the heat transfer fluid loses thermal energy. However, even the cooler, returning heat transfer fluid still contains thermal energy that can be stored for future use, and may also be stored in storage tank 26. Thus, storage tank 26 will have a temperature gradient that decreases from the top 58 of tank 26 to the bottom 60 of tank 26. To take advantage of this gradient, refrigeration output conduit 32 and thermal energy utilization output conduit 42 are connected toward top 58 of tank 26, such that the warmed fluid is returned from refrigeration unit 12 and is supplied to thermal energy utilization loop 40 from top 58 of tank 26. Similarly, refrigeration input conduit 34 and thermal energy utilization return conduit 44 are connected toward bottom 60 of tank 26 such that the cooled fluid is returned from thermal energy utilization loop 40 and supplied to refrigeration unit 12 from bottom 60 of tank 26. It will be understood that the same result may be obtained by using multiple tanks, with some holding cooler heat transfer fluid, and others holding warmer fluid.

It is unlikely that the heat supplied by refrigeration unit 12 will always be exactly the amount of heat required by the elements connected to thermal energy utilization loop 40. Other components are therefore included to ensure that system 10 maintains appropriate levels of thermal energy. An auxiliary heat source 62 is connected to thermal energy utilization output conduit 42 and thermal energy utilization return conduit 44, such that it acts as a bypass when more thermal energy is required by the heat transfer fluid being supplied to heat pumps 50. Circulation pump 36F circulates heat transfer fluid through auxiliary heat source 62. In addition, an auxiliary cooling source 64 is connected to refrigeration input conduit 34 and thermal energy utilization return conduit 44, such that it acts as a bypass when thermal energy needs to be removed from the heat transfer fluid. Temperature sensors 66 are included to determine the temperature of the heat transfer fluid. These sensors 66 may be positioned, for example, at the input to heat pumps 50, and two or more for determining the temperature of heat transfer fluid in storage tank 26, one toward top 58, and one toward bottom 60. Referring to FIG. 2, each of these elements: auxiliary heat source 62, auxiliary cooling source 64 and temperature sensors 66, are in communication with a controller 68. It will be understood that the description of the control system herein is at a base level, and those skilled in the art will recognize that controller 68 may provide other functions in addition to those described herein. Controller 68 is adapted to receive signals from temperature sensors 66, and activate auxiliary heat source 62 and cooling source 64. Thus, it provides supplementary heat from auxiliary heat source 62 when the temperature in the thermal energy utilization output conduit 42, as indicated by temperature sensors 66, falls below a predetermined temperature threshold, and provides supplementary cooling from auxiliary cooling source 64 when the temperature indicated by temperature sensors 66 rises above a predetermined temperature threshold. Circulation pump 36B circulates the heat transfer fluid through auxiliary cooling source 64.

Operation:

The use of thermal energy recovery system 10 as described above with reference to FIGS. 1 and 2 will now be discussed. Referring to FIG. 1, chiller 14 of refrigeration unit 12 is used to cool secondary refrigerant in a closed loop system, and is supplied to rink cold floor 19 to create and maintain an ice surface, and to dehumidifier 52, if present, by circulation pumps 36C and 36D. The warmed secondary refrigerant is returned to chiller 14 to be cooled again.

Heat transfer fluid is circulated by circulation pump 36A from bottom 60 of storage tank 26 via refrigeration input conduit 34, through condenser 16 to pick up the heat generated in cooling the refrigerant, in the form of low grade heat, and to top 58 of storage tank 26 via refrigeration output conduit 32. The position of conduits 32 and 34 allow cooler fluid to be supplied to condenser 16. Storage tank 26 stores the low grade heat generated by refrigeration unit 12 until needed by other devices.

When there is a demand for heating, such as from a thermostat 77 that is part of a building HVAC system 46, warmed heat transfer fluid is circulated by circulation pump 36E through thermal energy utilization output conduit 42 to heat pumps 50. These devices convert the low grade heat carried by the heat transfer fluid to high grade heat as needed. For example, return air 78 combines with outside air 80, passes through heat pump 50, which warms the air and is returned as supply air 82. The heat used to warm supply air 82 is taken from the heat transfer fluid, which is then returned to storage tank 26. If heat pumps are on the cooling cycle, then the heat removed from supply air 82 is transferred to the heat transfer fluid before being returned to storage tank 26.

To regulate the amount of thermal energy within system 10 as measured against a predetermined temperature range, temperature sensors 66, such as at the input to heat pumps 50 or on storage tank 26 are connected to controller 68, as shown in FIG. 2. Controller 68 activates either auxiliary heat source 62 or auxiliary cooling source 64 to either raise or lower the temperature, as needed. Referring again to FIG. 1, auxiliary heat source 62 acts as a bypass on storage tank 26, such that the heat transfer fluid returning in thermal energy utilization return conduit 44 is heated, and returned directly to thermal energy utilization output conduit 42, allowing the heat transfer fluid in storage tank 26 to be heated by refrigeration unit 12. Auxiliary cooling source 64 also acts as a bypass on storage tank 26 as it is connected from thermal energy utilization return conduit 44 to refrigeration input conduit 34. The heat transfer fluid is then cooled, such that less heat is returned to storage tank 26 after passing through condenser 16. This is one of several acceptable configurations. For example, the elements may also be in series rather than parallel as shown and described.

In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope defined in the Claims. 

1. A thermal energy recovery system for an ice making plant of an ice rink, comprising: a refrigeration unit for generating temperatures suitable for maintaining an ice surface and generating low grade heat as a by-product, the refrigeration unit having a fluid input and a fluid output; a storage tank for storing a heat transfer fluid; a refrigeration loop having a refrigeration output conduit connecting the fluid output of the refrigeration unit to the storage tank such that heat transfer fluid containing low grade heat from the refrigeration unit is conveyed to the storage tank, and a refrigeration input conduit connecting the fluid input of the refrigeration unit to the storage tank; at least one circulation pump on the refrigeration loop adapted to circulate heat transfer fluid from the storage tank through the refrigeration unit; a thermal energy utilization loop having a thermal energy utilization output conduit providing fluid communication from the storage tank to a building HVAC system, and a thermal energy utilization return conduit providing fluid communication from the building HVAC system back to the storage tank; at least one circulation pump on the thermal energy utilization loop adapted to circulate heat transfer fluid containing low grade heat from the storage tank through the building HVAC system; and at least one heat pump on the thermal energy utilization output conduit adapted to take heat transfer fluid containing low grade heat and convert the low grade heat into one of high grade heat or comfort cooling for use in the building HVAC system.
 2. The thermal energy recovery system of claim 1, further comprising at least one temperature sensor on the thermal energy utilization loop adapted to monitor a temperature of heat transfer fluid in the thermal energy utilization loop.
 3. The thermal energy recovery system of claim 2, further comprising an auxiliary heat source connected to the thermal energy utilization loop, and a controller in communication with the temperature sensor and the auxiliary heat source, the controller providing supplementary heat from the auxiliary heat source when the temperature in the thermal energy utilization output conduit, as indicated by the temperature sensor, falls below a predetermined temperature threshold.
 4. The thermal energy recovery system as defined in claim 3, further comprising an auxiliary cooling source connected to the thermal utilization loop, the auxiliary cooling source being in communication with the controller, the controller providing supplementary cooling from the auxiliary cooling source when the temperature indicated by the temperature sensor rises above a predetermined temperature threshold.
 5. The thermal energy recovery system as defined in claim 3, wherein the auxiliary heat source is connected to the thermal energy utilization output conduit and the thermal energy utilization return conduit, such that, when the auxiliary heat source is activated, the heat transfer fluid bypasses the storage tank.
 6. The thermal energy recovery system as defined in claim 4, wherein the auxiliary cooling source is connected to the thermal energy utilization return conduit and the refrigeration input conduit, such that, when the auxiliary cooling source is activated, the heat transfer fluid bypasses the storage tank.
 7. The thermal energy recovery system as defined in claim 1, wherein the at least one temperature sensor comprises a temperature sensor for determining the temperature at an input to the at least one heat pump, and at least one temperature sensor for determining the temperature in the storage tank.
 8. The thermal energy recovery system of claim 1, wherein at least one of a dehumidifier, an underfloor heater, and a snow melt pit is connected on the thermal energy utilization loop to the at least one heat pump.
 9. The thermal energy recovery system of claim 1, wherein the storage tank has a top and a bottom, the heat transfer fluid having a temperature gradient that decreases from the top of the tank to the bottom, the refrigeration output conduit and the thermal energy utilization output conduit being connected toward the top of the tank, and the refrigeration input conduit and the thermal energy utilization return conduit being connected toward the bottom of the tank.
 10. The thermal energy recovery system of claim 1, comprising one or more storage tanks.
 11. The thermal energy recovery system of claim 1, wherein the refrigeration unit comprises a chiller for removing heat from a refrigerant and a condenser for transferring the low grade heat to the heat transfer fluid.
 12. The thermal energy recovery system of claim 11, wherein the chiller receives warmed refrigerant from a cold floor to be cooled and returned to the cold floor.
 13. The thermal energy recovery system of claim 1, wherein the at least one heat pump has a heating mode and a cooling mode, such that in the heating mode the heat pump converts the low grade heat into high grade heat, and in the cooling mode the heat pump converts the low grade heat into comfort cooling.
 14. A thermal energy recovery system for an ice making plant of an ice rink, comprising: a refrigeration unit for generating temperatures suitable for maintaining an ice surface and generating low grade heat as a by-product, the refrigeration unit having a fluid input and a fluid output, the refrigeration unit comprising a chiller for removing heat from a secondary refrigerant and a condenser for transferring the low grade heat to a heat transfer fluid; at least one storage tank for storing a heat transfer fluid; a refrigeration loop having a refrigeration output conduit connecting the fluid output of the refrigeration unit to the storage tank such that heat transfer fluid containing low grade heat from the refrigeration unit is conveyed to the storage tank, and a refrigeration input conduit connecting the fluid input of the refrigeration unit to the storage tank; at least one circulation pump on the refrigeration loop adapted to circulate heat transfer fluid from the storage tank through the refrigeration unit; a thermal energy utilization loop having a thermal energy utilization output conduit providing fluid communication from the storage tank to a building HVAC system, and a thermal energy utilization return conduit providing fluid communication from the building HVAC system back to the storage tank; at least one circulation pump on the thermal energy utilization loop adapted to circulate heat transfer fluid containing low grade heat from the storage tank through the building HVAC system; at least one heat pump on the thermal energy utilization output conduit, the at least one heat pump having a heating mode and a cooling mode, in the heating mode the heat pump taking the heat transfer fluid and converting the low grade heat into high grade heat, and in the cooling mode the heat pump taking the heat transfer fluid and converting the low grade heat into comfort cooling; at least one temperature sensor for determining the temperature of the heat transfer fluid at an input to the at least one heat pump, and at least one temperature sensor for determining the temperature of the heat transfer fluid in the storage tank; an auxiliary heat source connected to the thermal energy utilization output conduit and the thermal energy utilization loop; an auxiliary cooling source connected to the thermal energy utilization return conduit and the refrigeration loop; and a controller in communication with the temperature sensors, the auxiliary heat source, and the auxiliary cooling source, the controller providing supplementary heat from the auxiliary heat source when the temperature in the thermal energy utilization output conduit, as indicated by the temperature sensors, falls below a predetermined temperature threshold, and the controller providing supplementary cooling from the auxiliary cooling source when the temperature indicated by the temperature sensors rises above a predetermined temperature threshold.
 15. A method of recovering thermal energy from an ice plant, the method comprising the steps of: circulating a heat transfer fluid through a refrigeration unit, the refrigeration unit transferring low grade heat to the heat transfer fluid; conveying heat transfer fluid containing low grade heat from the refrigeration unit to the storage tank; conveying heat transfer fluid containing low grade heat from the storage tank to a building HVAC system; operating at least one heat pump to convert the low grade heat into one of high grade heat or comfort cooling for use in the building HVAC system; and monitoring and controlling the temperature of the heat transfer fluid in the heat transfer utilization loop.
 16. The method of claim 15, further comprising the step of cooling the heat transfer fluid using an auxiliary cooling source when the temperature rises above a predetermined temperature. 